The function of a jaw crusher is based on a force which is compressing the rock. An eccentric shaft is attached to a body of the jaw crusher to which eccentric shaft is connected a movable jaw, i.e. a pitman, making an eccentric movement relative to a fixed jaw. For moving the pitman of the jaw crusher two main types are known in which two toggle plates, a so called double toggle, or one toggle plate, a so called single toggle, are used in the movement mechanism of the pitman.
In the double toggle type jaw crusher the eccentric shaft is connected between two toggle plates to move one end of the pitman (for example, a bottom end in a Blake-crusher) and a second end of the pitman is pivoted to the body of the crusher. In a double toggle crusher of a so called overhead pivot-type the pivot in the upper end of the pitman is located on a bisector of the crushing chamber wherein a stroke is formed in the upper portion of the crushing chamber which is larger than the stroke in the conventional Blake-crusher, and the stroke is in a more perpendicular direction relative to the fixed jaw. The stroke has a form of a large arc.
The single toggle type crusher is simpler than the double toggle type crusher. In the single toggle crusher one end of the pitman is pivoted through the eccentric shaft to the body of the crusher and the second end of the pitman is pivoted to the body of the crusher through the toggle plate. When the upper end of the pitman is pivoted by the eccentric shaft (a crusher of overhead eccentric type), a movement shape of the movable jaw is almost a circle in the upper portion of the crushing chamber because it is near the eccentric shaft. Then the stroke in the bottom portion of the crushing chamber has a form of a narrow ellipse and the movement shape is getting upwards more and more a form of a circle in the crushing chamber.
In the single toggle crushers the powerful stroke in the upper and centre portions of the crushing chamber is problematically short because of the form of the movement shape. A large part of the compression movement is directed inclined upwards or downwards. The amount of crushing strokes for breaking a single stone is high because of the short stroke what is limiting capacity and is leading to pulverizing of the surface of the material to be crushed before the actual crushing. Fine material is not interesting economically and generating of the fine material is causing unnecessary energy consumption. The direction of the stroke is not optimal in the bottom portion of the crushing chamber but is directed upwards wherein the material to be crushed is moving vertically on the wear surfaces. Large stones which require a relative long compression distance are crushed in the upper portion of the crushing chamber. The stroke length in the upper portion of the known crusher is small relative to the stone size. Because the stroke is short in the upper portion of the crushing chamber of the crusher, many strokes are required before large stones are broken. The unfavorable stroke direction is wearing the jaws more than a stroke which is perpendicular to the bisector of the crushing chamber.
In the double toggle crushers the shape and direction of the stroke are better than in the single toggle crushers. On the other side the stroke is much smaller in the upper portion than in the lower portion of the crushing chamber and so the upper portion of the crushing chamber becomes easy the part which is limiting the capacity.
When the jaws are wearing the nip angle in the crushing chamber is increasing and may in some applications drop the capacity of the crusher substantially smaller.
GB275100 shows a stone crusher with a fixed crushing jaw and a movable crushing jaw driven by an eccentric. The movable jaw is hung on pivots horizontally displaceable in slideways.
An object of the invention is to create an alternative crusher by which drawbacks present in connection with known crushers can be eliminated or at least reduced.